1. Field of the Invention
The present invention relates to processor controlled automatic wire bonders and more particularly to a new and improved workstation for use with semiconductor device holders or boats that support and position semiconductor devices over the workstation.
2. Description of the Prior Art
Automatic wire bonders are commercially available which provide different combinations of movable bonding heads and/or movable workstations. U.S. Pat. No. 4,266,710 shows a high speed vertically movable bonding head on an automatic ball wire bonder which cooperates with a workstation mounted on a movable X-Y table. Movable X-Y tables made and sold by Kulicke and Soffa Industries, Inc. of Horsham, PA may be adapted to support the bonding head mechanism or the workstation of an automatic wire bonder.
U.S. Pat. No. 4,239,144 shows a vertically moving bonding head for an automatic wedge wire bonder of the type employing a movable X-Y table for supporting a workstation. The wedge bonding head is movable in a rotary or theta direction to permit fine wire interconnections to be made between a first bond position on a semiconductor device and a second bond position or lead-out pad on a carrier or substrate in a radial direction.
These prior art automatic wire bonders move the workstation and workpiece in an X and Y direction relative to the bonding tool to form the wire bond interconnection. The semiconductor device is mounted on a workstation which is shown in a stationary position in a vertical axis.
The prior art automatic wire bonders complete the fine wire interconnection between the first and second bond in approximately 250 milliseconds which places acceleration forces of several times the force of gravity on the semiconductor on the workstation. The time required for positioning the semiconductor and the workstation on such X-Y tables is directly proportional to the mass of the moving tables and inversely proportionally to the forces being applied by the drive motors. Any increase in mass of the workstation will result in slowing down the time required to move the X-Y table and to complete a fine wire interconnection.
Holders (hereinafter called boats) and carriers for feeding a plurality of semiconductors to a workstation are known. When automatic loading and unloading machines are used in conjunction with automatic wire bonders, a large number of semiconductor devices may be wire bonded without the requirement of an operator or attendant to attend the machine and assure that individual semiconductor devices are properly positioned on the workstation prior to the bonding operation.
Prior art attempts to incorporate fast acting loading and unloading machines into the moving parts of an automatic wire bonder have not been satisfactory because the mass of the loading and unloading machine components becomes part of the mass of the moving parts of the wire bonders and slows down the operation of the wire bonder. Attempts to use auxillary robots or automatic pick up and placement machines have not been successful because extreme accuracy is required in the placement of the semiconductor devices on the workstations. Accurate robots and transfer devices are available but are relatively heavy and large which results in slowing the operation of the robot and/or transfer device and further are not suited for positioning small precision parts in the close confines of an automatic wire bonder.
It would be desirable to provide a low inertia workstation capable of loading and unloading semiconductor devices from a holder or boat at high speeds.
It would also be desirable to incorporate the loading and unloading mechanism of the workstation into an automatic wire bonder without slowing the operation of the wire bonding machine.